How to: factory auxiliary trans cooler upgrade

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SAATR

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As many of you know, the number one killer of automatic transmissions is heat. As temperatures rise, ATF loses its ability to effectively lubricate and cool the clutches, bands, and hard parts, resulting in slippage or outright failure. The 4L60E found in many of our trucks is no exception, and once you start adding things like big tires, higher stall torque converters, and power adders, the factory tranny cooling system becomes woefully inadequate. With this in mind, I decided to give the newly rebuilt 4L60E in my Suburban the best chance of survival that I can by upgrading the factory auxiliary cooler to a higher capacity aftermarket unit. I wanted a cooler with the greatest capacity possible that could still use the factory brackets and mounting location, seen here:

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The factory cooler is 11" wide, 5.75" tall, and 1.5" thick. Looking at the way the brackets are made, I figured it would be easier to trim to the upper bracket to size, so I whipped out the measuring tape again and discovered that the new cooler couldn't be more than 10" tall so as not to hit the center core support. After a little research, I came up with the B&M 70272, which measures 11" wide, 8" tall, and 1.5" thick, which was a perfect fit for the space I have. If I had it to do again, I would use the the B&M 70266, which is a black finish instead of polished (should have read more carefully, doh!), is built identically and is $30 cheaper. Live, learn, and don't get in a rush! Anyway, this is what arrived in the mail today:

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Now one major difference (besides the size) between these coolers is the fittings. The B&M's ports are 1/2" NPT, while the factory cooler uses a 3/8" NPTF port. To remedy this, you'll need two 3/8" by 1/2" NPT bushings which I purchase for two bucks each at AAP:

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To access the cooler, you first have to remove the grille shell and filler panel. Once those are off, you'll be staring right at the thing. Put a drain bucket (or old pot, as in my case) under the cooler and remove the covers and retaining clips from the quick connectors. Wiggle one line loose and let the fluid drain out of the line and the cooler. While it's draining, get a 10mm socket or nut driver and remove the bolts/screws holding the mounting bracket to the cooler and radiator support. Loosen the bolts holding the cooler to the lower bracket and tilt it toward the side that it's draining from, and go ahead and take the second line loose. Once the fluid flow is down to a dribble, take the lower mounting bolts out and remove the cooler from the truck. I would recommend sitting it in your drain pan and letting it finish draining.

Now grab your new cooler and loosely bolt it in to the lower bracket. The holes, oddly enough, line up perfectly, as you can see:

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I thought that the holes lining up just so had to be more than coincidence, so I inspected the coolers more closely. It turns out that the company that made the factory original, Long, also makes B&M's stacked plate coolers, as shown by the stampings:

Factory

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B&M

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Side by side

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Once you've bolted the cooler to the lower bracket, attach the upper bracket to the new cooler. The arms are far too long and overshoot the mounting holes by 3":

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So now we need to trim the arms down and drill our new mounting holes. I figured that trimming about 2.5" off of the each arm would make them short enough while leaving enough meat to bend the bracket back to the proper shape and drill new mounting holes. I will go ahead and say that somebody with a better equipped shop could have done a much prettier and more professional looking job of this, but I did what I needed to do with what I had. I measured approximately 2.5" from the top of each arm of the bracket ( approximate since it's actually bent, not straight) and marked it with soapstone. I then used a C-clamp to attach the bracket firmly to my workbench, where I used a reciprocating saw with a metal cutting blade to chop the arms down to size:

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Each bend in the bracket has a gusset stamped into it, and you'll actually be cutting through part of the gusset in the upper bend. I took a hammer and tapped the gusset flat, so that the trimmed bracket looks like the picture above. You'll want to use sandpaper or a file to deburr the cut, so it doesn't slice you to ribbons while installing it. Take your trimmed bracket back to the truck and check the fitment. Your bracket should touch the core support right above the screw holes. You'll need to bend the bracket back into its S shape so that the mounting pads will actually lay flush against the core support. I used the same C-clamp and an adjustable wrench to do it like so:

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The pads are about 3/4" long, but may vary depending on how you cut your bracket. Take the bracket back to the truck and check fitment again. The pads should center over the hole in the core support. Next, you'll need to drill the holes for your mounting screws, which I did using my trusty C-clamp and a scrap piece of 2x6. You'll want to use a minimum of a 1/4" bit, with 5/16" being preferable to allow some room for adjustments. Unfortunately, I did not make a pilot mark or hole, nor did I have a drill press, so my holes were not centered on the pads. If you have access to a drill press, use it! Otherwise, be very careful or your bracket will like something like this:

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The holes were actually close enough that they mounted up fine, but I would have preferred better accuracy. Anywho, you should now be able to dry fit your cooler. Like I said, the holes have enough movement to allow for less than perfect craftsmanship. Dry fitted it will look something like this:

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All you need to do now is install the adapter bushings and quick connects and you're ready to install it! Being that these are NPT fittings, they will require thread sealant to be leak free. I use Loctite 30561, but you can use any quality thread sealant that's rated for oil and high temperatures. Last, but not least, DO NOT OVERTIGHTEN THE FITTINGS!!! Pipe threads are tapered, and will not screw down flush like a bolt. Simply screw them in by hand until snug, then a little tighter using a wrench. This is what they look like, sans sealant:

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From this point, installation is the reverse of removal. You can't reuse the factory clips that hold the cooler lines to the lower bracket, so you may want to add a couple of discrete zip ties to support the lines. All you need do from here is start the truck and let run for a minute to circulate the fluid and then top it up as needed.

If you have any questions, post in this thread or PM me.
 
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monstar_est87

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Good write up broseph... Nice 2 see more out side the box thinkers posting useful information like this so every1 can benefit... Rep sent...
 

SAATR

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I hope it helps somebody. Most of us don't really think about what kind of stress our 4L60's are under until they puke. They can hold up to quite a bit, but you have to help em out a bit.
 

kidd666

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Great write up will be looking at doing this soon

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2
 

SAATR

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Great to have some real world numbers on the difference between the factory cooler and the upgrade. I don't have a trans temp gauge, so I had no idea that it was so significant. Glad I could be of some help!
 
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